JP2023117724A - Primer composition and coating film forming method - Google Patents

Abstract

To provide a primer composition that can be applied to between a substrate and a coating film so as to give excellent adhesion between the substrate and the coating film, and a coating film forming method capable of forming a coating film having excellent adhesion on a surface of the substrate.SOLUTION: A primer composition comprises a urethane-modified acrylic resin and colloidal silicas.SELECTED DRAWING: None

Description

The present invention relates to a primer composition and a film forming method.

BACKGROUND ART Conventionally, a chemical conversion film is formed on the surface of a base material such as a metal material, a ceramic material, or a resin material for the purpose of, for example, imparting rust prevention properties to the base material. Such chemical conversion coatings are required to have adhesion to substrates in consideration of long-term durability of rust prevention.

As a method of imparting adhesion to a base material to a chemical conversion film, for example, a primer layer is formed on the surface of a synthetic resin molded product from a primer composition containing a coating resin and an organosilicate compound, and a primer layer is formed on the primer layer. It is disclosed that a coating composition is applied to a surface to form an antifouling layer (see Patent Document 1).

However, Patent Document 1 discloses that the primer composition contains a coating resin such as an acrylic resin or a urethane resin, and an organosilicate compound. Adhesion of the above organosilicate compound is affected by the degree of hydrolysis, and there is a problem that the adhesion to the coating composition laminated on the primer layer is not sufficient.

Therefore, a primer composition capable of imparting excellent adhesion between the substrate and the coating by applying it between the substrate and the coating, and a coating excellent in adhesion on the substrate surface There is a demand for the development of a film forming method capable of forming

Japanese Patent Application Laid-Open No. 2003-105261

The present invention provides a primer composition that can impart excellent adhesion between a substrate and a film by applying it between the substrate and the film, and a primer composition that has excellent adhesion to the substrate surface. An object of the present invention is to provide a film forming method capable of forming a thin film.

As a result of intensive research, the present inventors have found that the above objects can be achieved by a primer composition containing a urethane-modified acrylic resin and colloidal silica, and a film-forming method using the primer composition. The discovery led to the completion of the present invention.

That is, the present invention relates to the following primer composition and film-forming method.
1. A primer composition containing a urethane-modified acrylic resin and colloidal silica.
2. Item 2. The primer composition according to Item 1, wherein the urethane-modified acrylic resin is a resin obtained by grafting a urethane component to an acrylic resin.
3. Item 3. The primer composition according to item 2, wherein the urethane-modified acrylic resin has a ratio of the urethane component of 10 to 80% by mass based on 100% by mass of the urethane-modified acrylic resin.
4. Item 4. The primer composition according to any one of Items 1 to 3, wherein the urethane-modified acrylic resin has a hydroxyl value of 0 to 150 KOHmg/g.
5. Item 5. The primer composition according to any one of Items 1 to 4, wherein the urethane-modified acrylic resin has a weight average molecular weight of 10,000 to 100,000.
6. Item 6. The primer composition according to any one of Items 1 to 5, wherein the colloidal silica is organic solvent-dispersed colloidal silica.
7. Item 7. The primer composition according to any one of Items 1 to 6, wherein the colloidal silica has an average particle size of 1 to 50 nm.
8. Item 8. The primer composition according to any one of items 1 to 7, wherein the content of the colloidal silica is 1 to 60 parts by mass based on 100 parts by mass of the urethane-modified acrylic resin.
9. A film forming method for forming a film on a substrate surface,
(1) Step 1 of applying a urethane-modified acrylic resin and a primer composition containing colloidal silica to the substrate surface to form a primer layer;
(2) Step 2 of applying a film-forming composition onto the primer layer to form a film-forming composition layer;
(3) having a step 3 of heating the film-forming composition layer to form a film having a silanol group;
The film-forming method, wherein the primer composition contains a urethane-modified acrylic resin and colloidal silica.
10. Item 9. An article having a primer layer comprising the primer composition according to any one of items 1 to 8.

The primer composition of the present invention can impart excellent adhesion between the substrate and the coating by applying it between the substrate and the coating. Moreover, the film forming method of the present invention can form a film having excellent adhesion on the substrate surface.

1. Primer Composition The primer composition of the present invention is a primer composition containing a urethane-modified acrylic resin and colloidal silica. In general, when a film having silanol groups is formed on the surface of a base material such as a metal material, a ceramic material, or a resin material, oxygen is generated by dehydration condensation between the hydroxyl groups on the base material surface and the silanol groups in the film. A covalent bond can be formed via and adhesion can be ensured. In the case of metal materials, ceramic materials, etc., adhesion to a film having silanol groups varies greatly depending on the amount of hydroxyl groups in the oxide film on the surface. In addition, there is a problem that adhesiveness cannot be ensured for resin materials such as ABS, PC, and PET, the resin component of which does not contain a hydroxyl group.

The primer composition of the present invention contains a urethane-modified acrylic resin excellent in adhesion to various materials constituting the substrate, and colloidal silica. Since the urethane-modified acrylic resin is a resin obtained by modifying an acrylic resin with a urethane component having excellent adhesion, the primer composition of the present invention can exhibit excellent adhesion to a substrate. In addition, since the primer composition of the present invention contains colloidal silica, it is possible to impart silanol groups to a primer layer formed using the primer composition, and a film having a silanol group formed on the primer layer It is possible to improve the adhesion with.

Furthermore, since the primer composition of the present invention contains colloidal silica, it is possible to impart an anchoring effect to the primer layer, thereby further improving adhesion to the film having a silanol group formed on the primer layer. can be done.

As described above, by using the primer composition of the present invention between the substrate and the coating, the substrate and the coating can be sufficiently adhered to each other.

Furthermore, by applying the primer composition of the present invention between the substrate and the film, the wear resistance of the film can be improved as compared with the case where the primer composition is not applied.

The present invention will be described in detail below.

(urethane-modified acrylic resin)
The urethane-modified acrylic resin is a resin having a structure obtained by modifying an acrylic resin with a urethane component.

The urethane-modified acrylic resin is not particularly limited as long as it has the above structure, but it is preferable to use a resin obtained by grafting a urethane component to an acrylic resin. Such urethane-modified acrylic resins are characterized by a structure in which a urethane moiety, which is a urethane component, is grafted onto an acrylic main chain made of an acrylic resin. may be

A commercially available product can be used as the urethane-modified acrylic resin.

The above urethane-modified acrylic resins may be used singly or in combination of two or more.

The urethane-modified acrylic resin has a urethane component ratio of preferably 10 to 80% by mass, more preferably 15 to 60% by mass, and even more preferably 20 to 40% by mass, based on 100% by mass of the urethane-modified acrylic resin. By setting the lower limit of the ratio of the urethane component within the above range, it is possible to impart even better adhesion between the substrate and the film. When the upper limit of the ratio of the urethane component is within the above range, cracks in the primer layer are further suppressed.

The hydroxyl value of the urethane-modified acrylic resin is preferably from 0 to 150 KOHmg/g, more preferably from 10 to 80 KOHmg/g, and even more preferably from 30 to 70KOHmg/g. When the lower limit of the hydroxyl value is within the above range, it is possible to impart even better adhesion between the substrate and the film. When the upper limit of the hydroxyl value is within the above range, the water resistance of the primer layer is further improved.

The weight average molecular weight of the urethane-modified acrylic resin is preferably 10,000 to 100,000, more preferably 20,000 to 80,000, even more preferably 30,000 to 50,000. When the lower limit of the weight molecular weight is within the above range, it is possible to impart even better adhesion between the substrate and the coating. When the upper limit of the weight molecular weight is within the above range, the coatability of the primer composition is further improved.

The content of the urethane-modified acrylic resin in the primer composition is preferably 0.5 to 60% by mass, more preferably 10 to 50% by mass, and even more preferably 15 to 45% by mass, based on 100% by mass of the primer composition. , 20 to 40% by weight are particularly preferred. By setting the lower limit of the content of the urethane-modified acrylic resin within the above range, it is possible to impart even better adhesion between the substrate and the film. When the upper limit of the content of the urethane-modified acrylic resin is within the above range, cracks in the primer layer are further suppressed.

(colloidal silica)
Colloidal silica is not particularly limited, and water-dispersed colloidal silica, hydrophobic colloidal silica, organic solvent-dispersed colloidal silica, and the like can be used. Among these, organic solvent-dispersed colloidal silica is preferable in terms of excellent dispersibility in the primer composition when the primer composition contains an organic solvent.

The average particle size of colloidal silica is preferably 1 to 400 nm, more preferably 1 to 100 nm, more preferably 1 to 50 nm, even more preferably 1 to 20 nm, and particularly preferably 5 to 15 nm. When the lower limit of the average particle size is within the above range, it is possible to impart even better adhesion between the substrate and the coating. When the upper limit of the average particle size is within the above range, the transparency of the primer layer is further improved.

Commercially available organic solvent-dispersed colloidal silica can be used.

The colloidal silica may be used singly or in combination of two or more.

The concentration of colloidal silica in the primer composition is not particularly limited. ∼65 parts by weight is more preferred, 1 to 60 parts by weight is particularly preferred, and 20 to 60 parts by weight is most preferred. When the lower limit of the concentration is within the above range, it is possible to impart even better adhesion between the substrate and the coating. When the upper limit of the concentration is within the above range, the occurrence of cracks in the primer layer and coating is further suppressed.

(Organic solvent)
The primer composition of the invention may contain an organic solvent.

The organic solvent is not particularly limited, and polar solvents, non-polar solvents, and the like can be used. Among these, a polar solvent is preferable from the viewpoint of excellent dispersion stability of colloidal silica particles.

Specific examples of organic solvents include alcohol solvents, glycol solvents, glycol ether solvents, ester solvents, and the like. Among these, alcohol-based solvents, glycol-based solvents, and glycol ether-based solvents are preferable, and these polar solvents are more preferable in terms of more excellent dispersion stability of colloidal silica.

Examples of alcohol solvents include methanol, ethanol, isopropyl alcohol, normal propyl alcohol, tertiary butanol, secondary butyl alcohol, 1,3-butanediol, 1,4-butanediol, 2-ethylhexyl alcohol, isobutanol, benzyl Alcohol etc. are mentioned.

Examples of glycol-based solvents include ethylene glycol, propylene glycol, diethylene glycol, triethylene glycol, and polyethylene glycol.

Glycol ether solvents include, for example, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monobutyl ether, ethylene glycol monomethyl ether, ethylene glycol monotertiary butyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, diethylene glycol monohexyl ether, dipropylene glycol methyl ether, triethylene glycol monomethyl ether, 3-methoxy-3-methyl-1-butanol and the like.

Examples of ester solvents include methyl acetate, ethyl acetate, butyl acetate, isobutyl acetate, methoxybutyl acetate, amyl acetate, normal propyl acetate, isopropyl acetate, methyl lactate, ethyl lactate, butyl lactate and the like.

The above organic solvents may be used singly or in combination of two or more.

The content of the organic solvent in the primer composition is not particularly limited. When the lower limit of the content of the organic solvent is in the above range, the stability of the primer composition is further improved, and excessive precipitation of colloidal silica on the substrate surface after coating can be suppressed. Poor appearance can be further suppressed. When the upper limit of the content of the organic solvent is within the above range, the adhesion between the substrate and the coating is further improved.

(other ingredients)
The primer composition of the present invention may contain other components in addition to the urethane-modified acrylic resin and colloidal silica. Other components include a cross-linking accelerator and the like.

As the cross-linking accelerator, an isocyanate compound, an organic metal compound, or the like can be used.

The content of other components in the primer composition is not particularly limited as long as it does not inhibit the effects of the present invention, and is preferably 10% by mass or less, and 5% by mass or less, based on 100% by mass of the primer composition of the present invention. is more preferable, and 1% by mass or less is even more preferable. Moreover, the lower limit of the content of other components is not particularly limited, and may be 0% by mass.

(Method for producing primer composition)
The method for producing the primer composition is not particularly limited. For example, the urethane-modified acrylic resin is added with the colloidal silica, and if necessary, the organic solvent and other components in the above-mentioned formulation. , and stirring.

The temperature of the primer composition during stirring is not particularly limited, and the stirring may be performed at room temperature of about 10 to 40°C. The stirring time is not particularly limited as long as the colloidal silica can be uniformly dispersed in the urethane-modified acrylic resin, and may be about 1 to 120 minutes.

(Goods)
The present invention also provides an article having a primer layer comprising the above primer composition. Examples of such an article include an article having a primer layer formed on the substrate surface by step 1 of the film forming method described below.

2. Coating Forming Method The coating forming method of the present invention is a coating forming method for forming a coating on the surface of a substrate, comprising:
(1) Step 1 of applying a urethane-modified acrylic resin and a primer composition containing colloidal silica to the substrate surface to form a primer layer;
(2) Step 2 of applying a film-forming composition onto the primer layer to form a film-forming composition layer;
(3) having a step 3 of heating the film-forming composition layer to form a film having a silanol group;
The primer composition is a film-forming method containing a urethane-modified acrylic resin and colloidal silica. Each step will be described below.

(Step 1)
Step 1 is a step of applying a primer composition containing a urethane-modified acrylic resin and colloidal silica to the substrate surface to form a primer layer. As the primer composition, the primer composition of the present invention described above may be used.

The substrate is not particularly limited, and examples thereof include metal materials, ceramic materials, and resin materials. A two-color molded article in which these materials are used in combination can also be used as the substrate.

The metal material is not particularly limited, and examples thereof include zinc, aluminum, magnesium, chromium, cobalt, nickel, iron, copper, tin, and alloys thereof.

The ceramic material is not particularly limited, and examples thereof include glass, alumina, zirconia, titania, ferrite, and enamel.

The resin material is not particularly limited, and examples include acrylonitrile-butadiene-styrene copolymer resin (ABS resin), resin in which the butadiene rubber component of ABS resin is replaced with acrylic rubber component (AAS resin), butadiene rubber component of ABS resin. is replaced with an ethylene-propylene rubber component (AES resin) and other styrene resins. In addition, alloyed resins of the above styrene-based resin and polycarbonate (PC) resin (for example, alloyed resins in which the mixing ratio of PC resin is about 30 to 70% by mass) are also included. In particular, an alloyed resin (PC/ABS resin) of an ABS resin and a polycarbonate resin, for example, a PC/ABS resin, which is an alloyed resin having a PC resin mixing ratio of about 30 to 70% by mass, can be used. Furthermore, polyphenylene ether resins, polyphenylene oxide resins, polybutylene terephthalate (PBT) resins, polyphenylene sulfide (PPS) resins, polyamide resins and the like are also included. A resin material obtained by subjecting the surface of the above resin material to metal plating such as chromium plating can also be used.

The method of applying the primer composition to the substrate surface is not particularly limited, and may be applied by known coating methods such as dip coating, spray coating, roll coating, spin coating and bar coating.

The coating amount of the primer composition on the substrate surface in step 1 is not particularly limited, and is preferably 10-1000 g/m ² , more preferably 50-500 g/m ² .

The thickness of the primer layer on the surface of the base material in step 1 is not particularly limited, and is preferably 1 to 10 μm, more preferably 2 to 5 μm.

A primer layer is formed on the substrate surface by the step 1 described above.

(Step 2)
Step 2 is a step of applying a film-forming composition onto the primer layer to form a film-forming composition layer.

The film-forming composition is not particularly limited as long as it can form a film having silanol groups by heating in step 3 described later. Examples of such film-forming compositions include film-forming compositions containing at least one selected from the group consisting of alkoxysilanes, silicic acid compounds, and silicone-modified resins, a catalyst, water, and a solvent. .

The above alkoxysilane is not particularly limited, and examples thereof include the formula: (R ¹ ) _m Si(OR ² ) _4-m (wherein R ¹ is a functional group, R ² is a lower alkyl group, m is 0). is an integer of ~ 3), and in the above chemical formula, the functional groups include vinyl, 3-glycidoxypropyl, 3-glycidoxypropylmethyl, 2-(3,4-epoxycyclohexyl)ethyl, p -styryl, 3-methacryloxypropyl, 3-methacryloxypropylmethyl, 3-acryloxypropyl, 3-aminopropyl, N-2-(aminoethyl)-3-aminopropyl, N-2-(aminoethyl)- 3-aminopropylmethyl, 3-triethoxysilyl-N-(1,3-dimethyl-butylidene)propylamine, N-phenyl-3-aminopropyl, N-(vinylbenzyl)-2-aminoethyl-3-amino Propyl, tris-(trimethoxysilylpropyl)isocyanurate, 3-ureidopropyl, 3-mercaptopropyl, 3-mercaptopropylmethyl, bis(triethoxysilylpropyl)tetrasulfide, 3-isocyanatopropyl, 3-propylsuccinic anhydride An example can be an object.

Specific examples of the lower alkyl groups include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, sec-butyl, n-pentyl, 1-ethylpropyl, isopentyl and neopentyl. A linear or branched alkyl group having about 1 to 6 carbon atoms can be mentioned.

Specific examples of the alkoxysilane represented by the above chemical formula include Si(OCH ₃ ) ₄ , Si(OC ₂ H ₅ ) ₄ , CH ₃ Si(OCH ₃ ) ₃ , CH ₃ Si(OC ₂ H ₅ ) ₃ , _C2H5Si ( _OCH3 ) ₃ , _C2H5Si ( _{OC2H5 ) 4 , CHCH2Si} ( _OCH3 ) ₃ , _{CH2CHOCH2O ( CH2} ) _3Si ( _{CH3O ) 3} , _CH2C ( _CH3 )COO( _CH2 ) _3Si ( _OCH3 ) ₃ , _CH2CHCOO ( _CH2 ) _3Si ( _OCH3 ) ₃ , _NH2 ( _CH2 ) _3Si ( _OCH3 ) ₃ , _SH ( _CH2 ) _3Si ( _CH3 ) ₃ , NCO( _CH2 ) _3Si ( _C2H5O ) ₃ may be mentioned.

The above alkoxysilanes can be used by mixing with resins such as urethane resins, epoxy resins, acrylic resins, polyester resins, melamine resins and silicone resins. Moreover, silicone-modified resins of these resins may be mixed and used, and among these, silicone-modified acrylic resins are preferable.

The above alkoxysilanes can be used singly or in combination of two or more.

The silicic acid compound is not particularly limited, and various known silicic acid compounds can be used. Specific examples of the silicate compound include lithium silicate, sodium silicate, potassium silicate, ammonium silicate, choline silicate, calcium silicate, magnesium silicate, hexafluorosilicic acid and the like.

The above silicic acid compounds can be used singly or in combination of two or more.

The silicone-modified resin is not particularly limited, and various known silicone-modified resins can be used. Specific examples of silicone-modified resins include silicone-modified resins such as urethane resins, epoxy resins, acrylic resins, polyester resins, and melamine resins. Among these, silicone-modified acrylic resins are preferred.

The film-forming composition preferably contains water and a catalyst. As a result, the alkoxysilyl groups are hydrolyzed, and a film having silanol groups can be formed in step 3 described later.

Acids, bases, organometallic compounds and the like can be used as catalysts.

Examples of the acid include hydrochloric acid, nitric acid, sulfuric acid, phosphoric acid, boric acid, formic acid, acetic acid, citric acid, oxalic acid and the like.

Examples of the base include potassium hydroxide, sodium hydroxide, ammonia, monoethylamine, diethylamine, triethylamine and the like.

As the organometallic compound, for example, a water-soluble organometallic chelate compound containing titanium, zirconium, aluminum, tin or the like as a metal component, a metal alkoxide, or the like can be used.

Among the above organometallic compounds, the organotitanium compounds include titanium alkoxide compounds such as tetraisopropyl titanate, tetra-normal butyl titanate, butyl titanate dimer, tetra-tert-butyl titanate, and tetraoctyl titanate; titanium diisopropoxybisacetylacetonate; Titanium tetraacetylacetonate, titanium dioctyloxybisethylacetoacetonate, titanium octylene glycolate, titanium diisopropoxybisethylacetylacetonate, titanium lactate, titanium lactate ammonium salt, titanium diisopropoxybistriethanolamine, etc. Examples include titanium chelate compounds. Examples of organic zirconium compounds include zirconium alkoxide compounds such as normal propyl zirconate and normal butyl zirconate; zirconium tetraacetylacetonate, zirconium tributoxymonoacetylacetonate, zirconium dibutoxybisethylacetoacetate, zirconium tributoxymonostearate and the like. and zirconium chelate compounds. Examples of organic aluminum compounds include aluminum alkoxide compounds such as aluminum isopropylate, monobutoxyaluminum diisopropylate, and aluminum butyrate; ethylacetoacetate aluminum diisopropylate, aluminum trisethyl acetate, alkylacetoacetate aluminum diisopropylate, aluminum monoacetyl Examples include aluminum chelate compounds such as acetonate bisethyl acetoacetate.

The above catalysts can be used singly or in combination of two or more.

The content of the catalyst is not particularly limited, and the film-forming composition is taken as 100% by mass. .

The content of water is generally about 0.1 to 50% by mass based on 100% by mass of the film-forming composition.

The solvent is not particularly limited as long as the alkoxysilyl group can cause hydrolysis and polycondensation reaction in an organic solvent. A ketone-based solvent or the like can be used.

The content of the solvent is not particularly limited as long as it can dissolve the above components, and may be about 1 to 95% by mass based on 100% by mass of the film-forming composition.

The method of applying the film-forming composition onto the primer layer is not particularly limited, and may be applied by known coating methods such as dip coating, spray coating, roll coating, spin coating and bar coating.

The coating amount of the film-forming composition in step 2 is not particularly limited, and is preferably 10-1000 g/m ² , more preferably 50-500 g/m ² .

A film-forming composition layer is formed on the primer layer by the step 2 described above.

(Step 3)
Step 3 is a step of heating the film-forming composition layer to form a film having silanol groups. By heating the film-forming composition layer in step 3, the solvent in the film-forming composition can be volatilized and a film having silanol groups can be formed.

The heating method is not particularly limited as long as the solvent of the film-forming composition layer formed in step 2 can be volatilized and a film having a silanol group can be formed, and the primer layer formed on the substrate surface. And the film-forming composition layer can be heated by a method such as a method in which the base material and the primer layer are placed in a constant temperature bath, a method in which the base material and the primer layer are placed in a dryer, and the like.

The heating temperature is preferably 20° C. or higher, more preferably 60° C. or higher. Moreover, the heating temperature is preferably 300° C. or lower, more preferably 250° C. or lower.

The heating time is not particularly limited, and is preferably 3 minutes or longer, more preferably 5 minutes or longer. Also, the heating time is preferably 120 minutes or less, more preferably 60 minutes or less.

The thickness of the film formed in step 3 is not particularly limited, and is preferably 50 μm or less, more preferably 30 μm or less. Moreover, the thickness of the film is preferably 0.1 μm or more, more preferably 0.5 μm or more. When the upper limit of the thickness of the coating is within the above range, the coating is transparent, and together with this, it is possible to impart more excellent anticorrosive properties to the substrate and to suppress deterioration of the appearance of the substrate. When the lower limit of the thickness of the coating is within the above range, it is possible to impart superior rust prevention to the substrate.

Through step 3 described above, the film-forming composition layer is heated to form a film having silanol groups.

EXAMPLES The present invention will be specifically described below with reference to examples and comparative examples. However, the present invention is not limited to the examples.

In addition, the following raw materials were prepared as raw materials used in Examples and Comparative Examples.

[Primer composition]
(resin component)
・Urethane-modified acrylic resin: urethane-modified acrylic resin grafted with a urethane component, ratio of urethane component in 100% by mass of urethane-modified acrylic resin: 30% by mass, hydroxyl value: 30 KOHmg/g, molecular weight: 40,000
・Acrylic polyol: hydroxyl value 60 KOHmg/g, molecular weight 50,000
・Acrylic polyol + isocyanate curing agent: Resin obtained by reacting acrylic polyol and isocyanate curing agent, hydroxyl value 60 KOH mg / g, molecular weight 50000

(colloidal silica)
・Colloidal silica with an average particle size of 10 nm: Organic solvent-dispersed colloidal silica ・Colloidal silica with an average particle size of 50 nm: Organic solvent-dispersed colloidal silica ・Colloidal silica with an average particle size of 100 nm: Organic solvent-dispersed colloidal silica

(Organic solvent)
・Propylene glycol monomethyl ether

[Film-forming composition]
(resin component)
・Silicone modified acrylic resin (solvent)
・Propylene glycol monomethyl ether

[Base material]
- Chrome-plated product: A treated product immediately after chrome-plating treatment and a treated product after 3 months of chrome-plating treatment were prepared.
・Glass ・ABS resin ・PC resin

(Preparation of primer composition)
100 g of resins shown in Tables 1 to 3 were prepared. With 100 parts by mass of the resin, colloidal silica and a solvent were prepared so as to have the formulations shown in Tables 1 to 3, and primer compositions of Examples and Comparative Examples were prepared using these. Specifically, the resin component was dissolved in propylene glycol monomethyl ether as a solvent, colloidal silica was added, and the mixture was stirred at 25° C. for 30 minutes.

(Preparation of film-forming composition)
Film-forming compositions of Examples and Comparative Examples were prepared according to the formulations shown in Tables 1-3. Specifically, a silicone-modified acrylic resin was dissolved in propylene glycol monomethyl ether as a solvent to prepare a film-forming composition.

(Formation of primer layer)
The primer composition was spray-coated on the surface of the base material at a coating amount of 100 g/m ² and allowed to stand at room temperature for 10 minutes to form a primer layer. The thickness of the primer layer was 3 μm.

(Formation of film-forming composition layer)
A coating amount of 200 g/m ² of the film-forming composition was spray-coated on the primer layer to form a film-forming composition layer. The thickness of the film-forming composition layer was 5 µm.

(Formation of film)
The film-forming composition layer was heated to form a film. Specifically, the base material and the laminate formed on the surface of the base material, in which the primer layer and the film-forming composition layer are laminated, are heated at 80° C. for 30 minutes using a constant temperature bath. to form a film. The thickness of the film was 10 µm.

The substrates on which the films were formed in the above Examples and Comparative Examples were evaluated as follows.

Adhesion Evaluation The adhesion of the film was measured by a measuring method based on JIS K 5600-5-6 and evaluated according to the following evaluation criteria.
○: Peeling occurred ×: Peeling did not occur

Appearance Evaluation The appearance of the laminate in which the primer layer and the film were formed on the substrate surface was visually observed from the film side, and crack generation and transparency were evaluated according to the following evaluation criteria.
(crack)
○: No cracks were observed △: Some cracks were observed ×: Cracks were observed on the entire surface (transparency)
○: was transparent △: was translucent ×: did not show transparency

The results are shown in Tables 1-3.

Claims (10)

A primer composition containing a urethane-modified acrylic resin and colloidal silica. The primer composition according to claim 1, wherein the urethane-modified acrylic resin is a resin obtained by grafting a urethane component to an acrylic resin. 3. The primer composition according to claim 2, wherein the urethane-modified acrylic resin has a ratio of the urethane component of 10 to 80% by mass based on 100% by mass of the urethane-modified acrylic resin. The primer composition according to any one of claims 1 to 3, wherein the urethane-modified acrylic resin has a hydroxyl value of 0 to 150 KOHmg/g. The primer composition according to any one of claims 1 to 4, wherein the urethane-modified acrylic resin has a weight average molecular weight of 10,000 to 100,000. The primer composition according to any one of claims 1 to 5, wherein the colloidal silica is organic solvent-dispersed colloidal silica. The primer composition according to any one of claims 1 to 6, wherein the colloidal silica has an average particle size of 1 to 50 nm. The primer composition according to any one of claims 1 to 7, wherein the content of said colloidal silica is 1 to 60 parts by mass based on 100 parts by mass of said urethane-modified acrylic resin. A film forming method for forming a film on a substrate surface,
(1) Step 1 of applying a urethane-modified acrylic resin and a primer composition containing colloidal silica to the substrate surface to form a primer layer;
(2) Step 2 of applying a film-forming composition onto the primer layer to form a film-forming composition layer;
(3) having a step 3 of heating the film-forming composition layer to form a film having a silanol group;
The film-forming method, wherein the primer composition contains a urethane-modified acrylic resin and colloidal silica. An article having a primer layer comprising the primer composition according to any one of claims 1 to 8.